Amyloidosis is a general term that describes a number of diseases characterized by the existence of pathological forms of amyloid proteins, often involving extracellular deposition of protein fibrils, which form numerous “amyloid deposits” or “amyloid plaques,” which may occur in local sites or systematically. These deposits or plaques are composed primarily of a naturally occurring soluble protein or peptide, assembled into extensive insoluble deposits 10-100 μm in diameter in a variety of tissue sites. The deposits are composed of generally lateral aggregates of fibrils that are approximately 10-15 nm in diameter. Amyloid fibrils produce a characteristic apple green birefringence in polarized light, when stained with Congo Red dye. Generally, the fibrillar composition of these deposits is an identifying characteristic for the various forms of amyloid disease.
The peptides or proteins forming the plaque deposits are often produced from a larger precursor protein. More specifically, the pathogenesis of amyloid aggregates such as fibril deposits generally involves proteolytic cleavage of an “abnormal” precursor protein into fragments that aggregate into anti-parallel β pleated sheets.
Systemic amyloidoses are a complex group of diseases caused by tissue deposition of misfolded proteins that result in progressive organ damage. The most common type, AL amyloidosis or primary amyloidosis, involves a hematological disorder caused by clonal plasma cells that produce misfolded immunoglobulin light chains. Overproduction of misfolded light chain by plasma cells results in deposits of abnormal AL protein (amyloid), in the tissues and organs of individuals with AL amyloidosis. Clinical features of AL amyloidosis include a constellation of symptoms and organ dysfunction that can include cardiac, renal, and hepatic dysfunction, gastrointestinal involvement, neuropathies and macroglossia. The mechanisms by which amyloidogenic immunoglobulin light chains result in organ dysfunction are not well characterized, however, it is hypothesized that both amyloid deposits and prefibrillar aggregates may contribute to cytotoxic effects on organs observed in patients with AL amyloidosis. AL amyloidosis is a disease entity of its own, although AL amyloidosis can occur concurrently in a small subset (up to 15%) of patients with multiple myeloma.
AL amyloidosis is a rare disorder with an estimated incidence of 8 in 1,000,000 people. Only 1200 to 3200 new cases of AL amyloidosis are reported each year in the United States. Two thirds of patients with AL amyloidosis are male and less than 5% of patients are under 40 years of age. Both the causes and origins of AL amyloidosis remain poorly understood.
Current treatment of patients with AL amyloidosis is aimed at reducing or eliminating the bone marrow disorder, i.e. the plasma cells that are responsible for producing the light chains, thereby limiting or halting the production of amyloid. The most aggressive treatment options include stem cell transplant and high-dose chemotherapy for those patients who can tolerate it. Other treatment regimens include combinations of drugs often used to treat hematological malignancies, such as melphalan, prednisone, dexamethasone and proteosome inhibitors such as bortezomib, in an attempt to reduce light chain production. There are no currently approved treatments for AL amyloidosis that directly target potentially toxic forms of the amyloidogenic proteins.
A different form of systemic amyloidosis, AA amyloidosis or secondary amyloidosis, occurs “secondarily” as a result of other illness, such as chronic inflammatory diseases (for example, rheumatoid arthritis and ankylosing spondylitis) or chronic infections (for example, tuberculosis or osteomyelitis). In secondary amyloidosis, the depositing amyloid protein is amyloid A protein, derived from an acute-phase protein serum amyloid A. The treatment of secondary amyloidosis is directed at treating the underlying illness.
Thus, there is a need for therapies to treat AA amyloidosis and AL amyloidosis, which directly target the pathological amyloid fibrils. The present invention provides pharmaceutical formulations of 2A4 and 7D8 antibodies, and chimeric and humanized versions thereof, which show high affinity binding to both AL and AA amyloids due to a shared immunogenic epitope of the pathological forms of these proteins.